Sensing And Imaging Based On The Photon Ic Spin Hall Effect

The photonic spin Hall effect is a phenomenon similar to the electron spin Hall effect.The left-handed and right-handed circularly polarization can be compared to the spin-up and spin-down electrons,and the refractive index gradient is similar to the role of the applied electric field.The specific process is:when the beam is reflected or refracted at the interface of two different media,with the change of propagation direction,the polarization vector of the different plane wave components in the beam is slightly rotated,which leads to the additional inconsistent geometric phase of the angular spectral component.Therefore,the spin angular momentum of the photon also changes.Spin angular momentum and orbital angular momentum together constitute the total photon angular momentum.Therefore,the change of spin angular momentum will induce the change of orbital angular momentum according to the law of conservation of total angular momentum,and finally the photon trajectory changes,which is manifested as the spin-dependent splitting of linearly polarized light.The photonic spin Hall effect is a sensitive effect,and the induced spin-dependent splitting shifts are tightly correlated to the physical parameters of the system.Because the small spin splitting shift of the photonic spin Hall effect is usually only a fraction of the wavelength,it is necessary to combine the weak measurement technology to achieve the obvious amplification of the initial weak signal,and the amplified displacement is closely related to the change of the preselection and postselection angles.Therefore,the photonic spin Hall effect is reasonable to be developed as a regulatory detection tool,which can show great application advantages in the field of biochemistry,such as optical sensors,precision instruments,etc.Moreover,the photon spin Hall effect has been found to achieve spatial optical differentiation for the incident light field,which is suitable for image edge detection and can retain valuable edge information for image processing.However,most of the current differ ential imaging based on the photonic spin Hall effect still stays at the stage of edge recognition of macroscopic intensity objects,while for the imaging at the microscopic level,for example,the transparent phase objects such as cells are rarely reported.In this dissertation,some characteristic applications are studied based on the photonic spin Hall effect.Novel chemical sensing technique was first developed based on the sensitivity of the photonic spin Hall effect.Further,the microscopic imaging of phase objects is realized by the optical differential operation based on the photonic spin Hall effect.This dissertation expands the application value of photonic spin Hall effect in sensing and imaging field.The main research contents are shown as follows:1.The photonic spin Hall effect is proposed to achieve the ultrasensitive and real-time detection of chemical reaction rate.Taking sucrose hydrolysis as an example,the optical rotation angle in the system will change with the reaction,and this changing rotation angle is regarded as postselection state.By incorporating with the weak-value amplification technology,the amplified displacement measurement pointer is used to monitor the real-time chemical reaction process,and eventually the measurement resolution with1.25×10^-4degree can be achieved.Experimentally,different concentrations of dilute hydrochloric acid were further selected as catalysts,and the reaction rate constant at different catalyst concentrations was indirectly obtained by using the change of spin-dependent splitting shift.This scheme does not involve any mechanical adjustment of the optical elements once the experimental setup is established and thereby realizes a real-time detection of the dynamic chemical reaction.2.The applications of chiral sensing and edge imaging are investigated using the photonic spin Hall effect based on computing metasurfaces.Firstly,we explain the differential imaging principle of the proposed scheme,and then establish the corresponding relationship between the preselected angle and amplified shift by the weak value amplification technique.It is found that when the optical rotation angle of the chiral object in the system has slight change,the weak-value amplification increases,and the field centroid changes significantly,which is finally manifested as an asymmetric edge-enhanced image.In experiment,different chiral objects with different concentrations are measured,respectively,which proves that high-contrast chiral recognition can be realized by edge detection.The results of this study provide a simple and accurate method for the identification and analysis of chiral objects,which has potential applications in real-time chemical and biological reaction.3.Differential microscopy based on the photonic spin Hall effect is presented and demonstrated,which enables compact,high-contrast and low-cost phase image processing.By studying the physical mechanism of the photon ic spin Hall effect,it is found that tiny spin-dependent shift can perform an optical spatial differentiation operation on the phase distribution,which offers an effective way to visualize phase objects.We experimentally demonstrate the superiority of our scheme for edge-enhanced detection of phase-resolution targets and unlabeled biological cells.Moreover,different wavelengths were selected for experiments,and the experimental results demonstrate the wavelength independence of the scheme.Finally,the phase distribution was recovered by biased microscopy imaging of samples with different phase gradients,which provides a simple way for quantitative analysis of phase images.4.By combining the Brewster effect and the spin-orbit interaction of light,we propose differential microscopy for spatial two-dimensional differential imaging,which overcomes the limitation of conventional one-dimensional imaging.Through imaging experiments on phase microscopy target,the results show that the proposed microscopic imaging scheme achieves high-resolution phase-contrast imaging and is sensitive to different phase gradients.Furthermore,the capability of the system for nondestructive imaging of transparent biological samples is also verified.The results indicate that our research provides opportunities for label-free and high-resolution bioanalysis.